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Arrhenatherum

Arrhenatherum* P. Beauv.,. Essai Agrost. 55,
152, 153 (1812).

Derivation:.
From Greek arrhenos (male) and ather (awn), alluding to the male
florets accompanying the fertile ones.

Key references
(keys and floras):
. G.Bentham, Flora Australiensis 7: 586(1878);
C.A.Gardner, Flora of Western Australia 1 Gramineae 39–40 (1952);
J.C.Tothill and J.B.Hacker, Grasses of Southern Queensland 110–111
(1983); J.P.Jessop, Flora of South Australia 4: 1909(1986); B.K.Simon, Key
to Australian Grasses
73 (1993); S.W.L.Jacobs and S.M.Hastings, Flora of
New South Wales
4: 589–590 (1993); N.G. Walsh, Flora of Victoria 2:
448–449 (1994); D.I.Morris, Student's Flora of Tasmania 4B:
234–235 (1994); E.Edgar and H.E.Connor, Flora of New Zealand 5: 299–301
(2000); D.Sharp and B.K.Simon, AusGrass (2002); J.P.Jessop, Grasses
of South Australia
202 (2006); S.W.L.Jacobs, R.D.B.Whalley &
D.J.B.Wheeler, Grasses of New South Wales, 4th Ed, 133 (2008); A.Wilson
(ed.), Flora of Australia 44A: Poaceae 2: 127–128 (2009)

W.D.Clayton &
S.A.Renvoize, Genera Graminum (1986), genus (172).

Naturalised. 4
species, from Europe, Mediterranean. 1 species in Australia, SA, Qld, NSW, Vic,
and Tas. Also New Zealand.

Habit.
Perennial (often with globose corms at base), tufted. Leaf blades narrow.
Ligule an unfringed membrane (sometimes puberulent).

Inflorescence.
Inflorescence paniculate, a spike-like panicle, contracted.

Spikelets.
Spikelets laterally compressed, 2 flowered to more than 2 flowered, with 1
fertile floret, awned, solitary, pedicelled; with naked rachilla extension.
Fertile spikelets with lower incomplete floret(s) or without lower incomplete
floret(s) (rarely), disarticulating above glumes (the florets falling together).

Glumes. Glumes
unequal, about equal to spikelet to exceeding florets, long relative to
adjacent lemmas, pointed, awnless, keeled or non-keeled, similar (membranous).
Lower glume 1–3 nerved. Upper glume 3 nerved.

Florets. Lower
incomplete floret(s) male. Lemmas awned (the awn geniculate, from the lower
back), 5–9 nerved, more or less equalling fertile lemmas, similar in texture to
fertile lemmas (firmly membranous to subcoriaceous), not becoming indurated.
Fertile florets 1 (or rarely 2–4). Lemmas decidedly firmer than glumes, not
becoming indurated, entire at apex or incised, muticous or awned, without a
germination flap, 5–9 nerved, hairy or glabrous. Awns when present, 1, dorsal,
non-geniculate (usually short and slender), much shorter than body of lemma to
about as long as body of lemma. Palea relatively long, apically notched
(shortly bidentate), 2 nerved. Distal incomplete florets 1 (if present),
underdeveloped. Callus short. Lodicules 2. Stamens 3. Grain small to large,
compressed dorsiventrally to terete, hairy on body. Hilum long-linear. Embryo
small.

Kranz Anatomy.
C3.

2n = 14,
28, and 42, 2, 4, and 6 ploid, commonly adventive.

Habitat.
Mesophytic to xerophytic. Dry grassland, edges of woods, disturbed ground.
Species of open habitats.

Classification.
Pooideae; Poeae.

Notes. A
segregate from Helictotrichon with dimorphic florets. However the degree
of dimorphism varies considerably, even within the same panicle, and the
distinction is barely tenable (Clayton and Renvoize, 1986).

Types Species. A.
avenaceum
P.Beauv., nom. illeg. = Avena elatior L.

Biogeographic
Element
. Clifford & Simon 1981, Simon & Jacobs 1990: Naturalised.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith